Currently, standardization of a 4G radio communication system is under progress by 3GPP (Third Generation Partnership Project). According to the 4G, an improvement in maximum communication speed and a quality improvement in cell edges can be realized by using technologies such as relays and carrier aggregation. Further, considerations are given to improving coverage by introducing base stations other than eNodeB (macro-cell base station), such as HeNodeB (Home eNodeB, femtocell base station, compact base station for cell phones) and RHH (Remote Radio Head).
(Blind Decoding)
In a radio communication system as above, the base station notifies an assignment of a receiver resource to a UE (Downlink Assign), a grant of a transmitter resource (Uplink Grant) and the like by a control signal called PDCCH (Phy Downlink Control Channel). Here, resource information such as the Downlink Assign and the Uplink Grant are information for each UE (User Equipment). Due to this, the base station transmits the control signal so that each UE can extract the resource information addressed to itself, and each UE extracts the resource information addressed to itself from the PDCCH by a process called blind decoding. Hereinbelow, this feature will be described in detail.
The base station describes resource information addressed to each UE in smallest units of the control signal called CCE (Control Channel Element). Further, the base station adds, to the CCE, check bits that are obtained by CRC (Cyclic Redundancy Check) by masking the resource information with C-RNTI (Cell Radio Network Temporary Identify) that is an identifier unique to each UE.
When the PDCCH including a plurality of the aforementioned CCEs is received, the UE performs the CRC check by demasking each CCE by the UE's own C-RNTI. That is, the UE performs the CRC check of each CCE on an assumption that each CCE is addressed to itself, and determines the CCE with a normal result as the CCE addressed to itself. The above process by the UE is called the blind decoding, and such a blind decoding is described for example in Patent Literature 1.
(MTC)
On the other hand, debates on MTC (Machine Type Communications) are also in progress in the 3GPP. The MTC is generally synonymous to M2M (Machine to Machine), and refers to a communication between machines and not directly used by a human. The MTC primarily is performed between a server and a MTC terminal that is not directly used by a human.
For example, as a medical application of the MTC, a case may be assumed in which an MTC terminal collects electrocardiogram information of a human, and transmits the electrocardiogram information to a server by using uplink when a certain trigger condition is met. As another application of the MTC, a case may be assumed in which a vending machine is caused to function as an MTC terminal, and a server causes the vending machine under management to report sales once every certain cycle (for example, every 30 days).
Such an MTC terminal by way of example has the following features in general, however, not every MTC terminal needs to have all of the following features, and which of the features is to be endowed depends on applications.
Scarce needs to move (Low Mobility)
Transmission of small data (Online Small Data Transmission)
Very low power consumption (Extra Low Power Consumption)
Handled by grouping respective MTCs (Group-based MTC Features)